Field of the Invention
The present invention relates to communication devices, communication systems and a computer readable medium.
Description of the Related Art
HTTP (Hyper Text Transfer Protocol) is one example of a protocol (communication protocol) in wide use as an Internet standard technique. The Internet Engineering Task Force (IETF) has recently developed a new version of HTTP (HTTP/2). HTTP/2 adds new functions while maintaining compatibility with the existing technology of HTTP 1.1. For example, HTTP/2 is capable of establishing multiple streams, which are bi-directional flows of frames across a virtual channel, within a single connection. An HTTP request/response is allocated to a single stream, and one stream is independent from other streams, which means that request blocks, terminations, and so on do not interfere with the progress of other requests.
To handle a connection termination caused by networks firewalls, PPPoE or NAT timeouts, or the like, or in other words, caused by a non-communication state continuing for more than a set amount of time, a technique has been proposed in which a packet is sent to a server device to maintain a connection when a non-communication state in the connection has reached a predetermined amount of time, and the predetermined amount of time is shortened when it is detected that packets are not being communicated (Japanese Patent Laid-Open No. 2014-199998).
The technique disclosed in Japanese Patent Laid-Open No. 2014-199998 does not take into consideration control for maintaining a connection in communication where at least two streams are established on the connection. As such, in the case where streams are independent from each other in a single connection as described above and a single stream is being communicated on a given connection, there have been cases of unnecessary communication arising to maintain the connection in other streams.